1. Field of the Invention
The present invention relates to an improved controlled release carrier system that can be incorporated into soap bars that enhances deposition of active ingredients as well as fragrances onto skin and which prolongs the release of active ingredients and fragrances from the skin over an extended period of time.
2. Description of the Related Art
Consumer acceptance of soap bars is determined not only by the performance achieved with these products but the aesthetics associated therewith. Fragrance is an important aspect of the successful soap bars and they are being utilized, in addition to imparting an aesthetically pleasing odor, to convey to the consumer the product performance and effectiveness (i.e., the skin is clean, etc.). Recently, soap bars are utilized not only to clean and disinfect the skin, but also to impart long lasting malodor coverage and the performance features expected from these products are similar to those of deodorants.
Fragrances are typically added to soap bars to provide a fresh, clean impression for these products as well as the skin treated with these products. While the fragrance does not add to the performance of soap bars, it does make these products more aesthetically pleasing and the consumer has come to expect such products to have a pleasing odor. The fragrance plays a major, and often determining, role for the consumer in selecting and purchasing the soap bars. Consumers are becoming increasingly educated and expect a high level of sophistication in their soaps. Many consumers would prefer for the fragrance or the disinfecting actives, present in these products, to be deposited on the skin and remain there for an extended period of time to convey a lasting impression of freshness. Fragrance creation for soaps is restricted not only by considerations such as availability and cost, but also by compatibility of the fragrance ingredients with other components in the product composition and the ability of the fragrance ingredients to deposit onto the skin and survive the rinse process. Furthermore, large amount of fragrance is being lost during washing. Practice has shown that when currently available products are used, a large fraction of the fragrance is lost during the rinse process due to the solubility of certain fragrance ingredients in aqueous washing compositions, and the fraction of the fragrance which was deposited, quickly evaporates, due to the volatility of fragrance ingredients.
Water soluble polymers have also been used to encapsulate fragrance oils. Such capsules have proved useful in releasing perfume in deodorants. However, such capsules have not been commercially successful in extended release of perfume from skin. U.S. Pat. Nos. 5,770,556 and 5,955,409 disclose a process for making bar compositions having enhanced deposition of benefit agent. The patents relate to a process in which specific powder adjuvants comprising (a) benefit agents, (b) a carrier (e.g., soluble or partially soluble starches, water soluble amorphous solids or semi-crystalline water soluble solids), (c) water and (d) optional deposition/processing aids are first prepared and then mixed with bar chips prior to milling, extruding and stamping the bars. The carrier component disclosed by U.S. Pat. No. 5,770,556 is any water soluble starch including both partially soluble starches (such as corn or potato starch) and, more preferably, “true” water soluble starches, i.e., starches in which at least 10% by wt. or greater solution of starch in water will dissolve to form a clear or substantially clear solution. Examples of such include maltodextrin. The carrier may also be a semi-crystalline water soluble solid such as, for example, gelatin. The carrier compound generally will comprise about 15% to 98%, preferably 30% to 50% of the powder composition. These carrier materials will quickly dissolve in water (especially maltodextrins) to release the active and have little chance to enhance deposition of active ingredients onto the skin and sustain their release rate on the skin.
U.S. Pat. No. 5,876,755 discloses a water-sensitive matrix material which can be starch, modified starch, maltodextrin, cyclodextrin, gums, resins, synthetic or semisynthetic polymers such as polyvinyl pyrrolidine (PVP), polyvinylalcohol (PVA) and cellulose esters, and combinations of these materials. The preferred matrix material comprises modified starch. The encapsulating material (i.e., the encapsulated substance within the water-sensitive matrix) is conveniently prepared by spray drying, and is typically particulate so that the composition as a whole is particulate in nature.
U.S. Pat. Nos. 4,803,195 and 5,508,259 also disclose a water soluble encapsulation system that can be incorporated in soap bars. The matrix material utilized in the above patents comprises:                a. a solid film-forming substrate chosen from polyvinyl acetate, polyvinyl alcohol, dextrins, natural or modified starch, vegetable gums, pectins, xanthans, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose and lipoheteropolysaccharides, and        b. an emulsifying agent chosen from mono- or diglycerides of fatty acids, esters derived from the combination of fatty acids with sorbitol or a saccharide, or their alkoxylated derivatives, or an ester of tartaric, citric, ascorbic or lactic acid.Again, these carrier materials will quickly dissolve in water (especially maltodextrins) to release the active and have little chance to enhance deposition of active ingredients onto the skin and sustain their release rate on the skin.        
U.S. Pat. No. 4,749,501 discloses a solid soap composition comprising a soap base and microcapsules dispersed therein, said microcapsules are prepared by using a hydrophobic liquid as a core material, forming microcapsules by covering the hydrophobic liquid with coacervate of a hydrophilic material, and then adding an electrolyte to a solution having the microcapsules dispersed therein in an amount of 8 to 100 parts by weight to 100 parts by weight of the water used in the microcapsules to dehydrate the microcapsule films. The hydrophilic coacervate is an anionic hydrophilic high molecular weight substance is gum arabic, alkali metal salt of carboxymethyl cellulose, sodium alginate, carrageenan, styrene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, acrylic acid copolymer, polyvinylbenzene sulfonic acid, carboxymethyl starch or mixtures thereof. The microcapsules hardly disintegrate during the soap production process but do disintegrate during the use of the soap composition when contacted with water. This type of controlled release system has the limitation of not working with all type of fragrance ingredients, especially not with fragrance ingredients that are relatively water-soluble and do not deposit into the skin.
A similar system is described in U.S. Pat. No. 6,248,703 which discloses bar compositions comprising a non-water soluble benefit agent core surrounded by a friable coating comprising the reaction product of (1) an amine selected from urea and melamine; and (2) an aldehyde selected from formaldehyde, acetaldehyde and glutaraldehyde; and mixtures of the amines and the aldehydes; wherein the capsules are strong enough to survive a soap extrusion process but sufficiently friable to break upon use of the bar by the consumer.
Perfumes have been adsorbed onto various materials such as silica and cyclodextrins to deliver perfume in soap bars. U.S. Pat. No. 5,723,420 discloses a personal cleansing bar compositions which contains a fragrance-releasing complex and a bar carrier. The fragrance-releasing complex contains a hydrophilic inorganic porous fragrance carrier and a fragrance impregnated within the fragrance carrier. Inorganic carriers include amorphous silica, precipitated silica, fumed silica and aluminosilicates such as zeolite and alumina. Another type of inorganic carrier suitable for use in the present invention include cyclodextrin. This system has the drawback that the fragrance oil is not sufficiently protected and is frequently lost or destabilized during processing.
Attempts to enhance deposition of fragrance onto skin have been described in U.S. Pat. No. 5,476,660 which discloses compositions to deposit an active substance on a target surface. The active substance is left on the surface after the product is rinsed off the surface. The preferred deposition is from compositions containing an anionic or nonionic active in the co-presence of an anionic surfactant. The compositions contain carrier particles having a zwitterionic or cationic surface and a plurality of outwardly protruding filaments containing charged organocarbyl groups. The term “zwitterionic” as described in this patent means a mixture of cationic and anionic (not necessarily neutral); thus the surface of the zwitterionic particles, have both cationic and anionic groups (i.e., positively charged and negatively charged organocarbyl groups). The filaments are formed from an emulsion comprising molten wax, an anionic surfactant and a cationic surfactant. The active substance is contained within the carrier particles.
The major challenge in designing controlled delivery systems for soap bars is maximizing the deposition of the system comprising the active ingredients onto the skin. There remains a need in the art for an efficient controlled delivery system, to effectively deposit active ingredients, as well as fragrances, onto skin and for a method to “boost” the overall charge density of particles thereby providing enhanced deposition onto the skin.
The prior art of which applicant is aware does not set forth a fragrance controlled release system that can be incorporated in a soap bar to enhance deposition of active ingredients, as well as fragrances, especially not for fragrance ingredients that are more soluble into the aqueous phase of the washing compositions and do not deposit onto the skin. There is also a need for a fragrance carrier system, for soap bars, that will allow using a wider range of fragrance ingredients that are currently not substantive on skin from a soap bar application and improved fragrance substantivity and longevity onto the skin. It is desirable to provide a control release system for overcoming these limitations. It is also desirable to provide a method using an efficient and economical process for effectively delivering a broad range of fragrances and other ingredients onto skin and yields a high impact fragrance “burst” upon washing and a prolonged fragrance release from the skin over an extended period of time.